Ozone-induced changes in physiological and biochemical traits in Elaeocarpus sylvestrisandMichelia chapensisin South China

Özet

The influences of elevated ozone (O3) concentrations on biomass, leaf gas exchange,fluorescence parameters,and leaf physiological and biochemical traits were examined inElaeocarpus sylvestris and Michelia chapensisseedlings under four O3conditions for a growing season in open-top chambers (OTCs). The four O3con-centrations were charcoal-filtered air (CF) (20 ppb), 1 × O3air (40 ppb), 2 × O3air (80 ppb), and 4 × O3air(160 ppb), respectively. The significant decrease in the root/shoot (R/S) ratios of both species indicated thatunder O3stress root biomass was more negatively affected than shoot biomass for both tree seedlings. Along withthe loss of chlorophyll and carotenoid contents, decrease in the superoxide dismutase (SOD), and enhanced levelof lipid peroxidant, the light-saturated net photosynthesis rate (Pnmax)ofE. sylvestris, the effective quantum yieldof PSII photochemistry (Y(II)) and the electron transport rate (ETR) of both species decreased, suggesting thatimpaired photosynthesis occurred. The negative effect of O3on physiological and biochemical parameters wasgreater forM. chapensisthan forE. sylvestris. As the O3concentration increased, the leaf mass per area (LMA) ofE. sylvestrisdecreased, while that ofM. chapensisincreased. Therefore, the increased SOD activity as a hormetic-compensatory response, the increases in LMA and longer vegetative period contributed to the good adaptabilityand high tolerance ofM. chapensis.